Imaging x-ray detectors are employed for the spatially resolved detection of x-ray radiation in materials analysis, in security checks and quality assurance inspections, as well as in the medical technology field. An x-ray detector of the type typically comprises a number of pixel-like detector elements which are arranged for example as a two-dimensional detector array.
There are direct-converting detector elements and indirect-converting detector elements. Whereas a direct-converting detector element converts the impinging x-ray radiation directly into an electrical signal, in the case of an indirect-converting detector element the x-ray radiation is initially converted into low-energy (in comparison with x-ray radiation) electromagnetic radiation in the visible, infrared or ultraviolet spectral range (light). For this purpose, an indirect-converting detector element comprises a layer composed of scintillating material which absorbs incident x-ray beams and emits (scintillation) light. The scintillation light is detected by means of a photoactive element, such as a photodiode, for example, and converted into an electrical signal.
Organic photodiodes are used increasingly as photoactive elements owing to the fact that the organic semiconductor materials utilized for this purpose absorb the scintillation light better than inorganic semiconductor materials. An organic photodiode of the aforesaid type typically comprises a photoactive organic absorption layer which is arranged between an electrode and a counter electrode.
WO 2012/062625 A2 discloses a hybrid structure for a detector element in which the scintillation layer and the photoactive layer are combined to form a common hybrid layer. The hybrid layer arranged between an electrode and a counter electrode is formed from a photoactive absorption layer composed of organic semiconductor material in which a plurality of scintillator particles are embedded. However, experience shows that in order to achieve an adequate degree of x-ray absorption, the hybrid layer of such detector elements must have a minimum thickness of typically about 100 μm.